[FpUser]

Something like Microsoft does with the their interfaces

They have multiple versions of calls. The older one function as before and never change. Want different behavior - here is your_interface_v1(), your_interface_v2(), etc.

You still alert team about new functionality but they're free to consume it at their own pace. This of course involves a boatload of design and planning.

I am in general against microservices and consider those as the last resort when nothing else works. To me a microservice is mostly my monolith interacting with another monolith.

When monolith becomes big enough that it needs 2 teams I usually handle it by each team releasing their part as a library that still gets linked into the same monolith. That is my version of "microservice" when the only reason for it to exist is to have two or more "independent" teams.